堆石料状态相关三维多重机制边界面模型

堆石料的应力应变特性与材料的密度、压力等状态密切相关。针对堆石料的变形与强度非线性,在临界状态和边界面弹塑性理论框架内,建立了一个堆石料状态相关三维多重机制边界面模型。模型将复杂的宏观变形行为分解为一个宏观体应变机制和一系列空间分布的相互独立虚拟微观剪切机制。每个微观剪切机制包含3个方向的微观剪应力–应变关系和微观应力–剪胀关系。引入一个与密度、压力相关的状态参数,用以统一描述不同状态下堆石料的变形和强度特性。模型包含12个参数,多数具有明确的物理意义。对2种堆石料三轴压缩试验结果进行模拟计算,模型模拟值与试验结果吻合良好,说明模型能够较合理地预测堆石料的应力应变特性。

State-dependent 3D multi-mechanism bounding surface model for rockfills

The rockfill materials have been widely used in the construction of rock?ll dams due to their high strength, small deformation and strong permeability. The strength and deformation characteristics of the rockfill materials are essential prerequisites to the design of rock?ll dams. The existing laboratory tests have shown that the stress-strain relation of the rockfill materials is closely related to their states in density and pressure. Within the framework of the critical state and bounding surface plasticity theories, a state-dependent 3D multi-mechanism bounding surface model is proposed for the rockfill materials by considering their nonlinear characteristics in deformation and strength. The macroscopic deformation behaviors of the rockfill materials in this model are decomposed into a macroscopic volumetric mechanism and a set of independent virtual microscopic shear mechanisms in spatially distributed orientations. Each microscopic shear mechanism is described by the microscopic shear stress-strain relations and microscopic stress-dilatancy relations in three directions. A state parameter is introduced in the strength criterion and stress-dilatancy relation for compatibility with the critical state theory. Some relations are established between the microscopic and macroscopic model parameters. The model has twelve parameters, and most of them are of clear physical meanings. The proposed model is used for simulating the triaxial compression tests on two types of rockfill materials. The results show that the calculated values are in good agreement with the test data, indicating that the proposed model is capable of predicting reasonably the strain-hardening and strain-softening behaviors of the rockfill materials under different densities and confining pressures.